body {
    background: linear-gradient(to right, #85D8CE, #085078); 
  }

  #app {
    font-family: 'Avenir', Helvetica, Arial, sans-serif;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    text-align: center;
    color: #2c3e50;
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    align-item: center;
  }  
.calculator {
    width: 440px;
    padding: 20px;
    border-radius: 5px;
    margin: 20px auto;
    font-size: 16px;
    background-color: hsl(0, 0%, 20%);
  }

  .input {
    width: 420px;   
    height: 50px;
    border-radius: 0px;
    border: 1px solid hsl(0, 0%, 0%);
    background-color: #333333;
    color: #d9d9d9;
    padding: 0 5px 0 5px;
    margin: 0 0px 10px 0px;
    font-size: 30px;
  }

  .input:focus,
  .input:active {
    border-color: #03a9f4;
    box-shadow: 0 0 4px #03A9F4;
    outline: none 0;
  }

  .button {
    margin: 3px;
    width: 63px;
    border: 1px solid hsl(0, 0%, 5%);
    height: 30px;
    border-radius: 4px;
    color: hsl(0, 0%, 85%);
    background-color: hsl(0, 0%, 10%);
    cursor: pointer;
    outline: none;
  }

  .mode {
    display: flex;
    flex-wrap: wrap;
    justify-content: space-evenly;
  }

  .equal-sign {
    background-color: hsl(120, 100%, 25%);
    width: 133px;
  }

  .toggle-button {
    border: none;
    background-color: hsl(0, 0%, 20%);
    cursor: pointer;
    outline: none;
    font-size: 1rem;
    color: #fff;
    text-shadow: -1px -1px 0 rgba(0, 0, 0, .35)
  }

  p {
    margin-top: 0;
  }

  button::-moz-focus-inner {
    border-color: transparent;
  }